BARCELONA, Spain--The smartphone screen on the iPhone above may look like it's made of glass, but it isn't. It's made of sapphire. That's right, the same aluminum oxide compound (AL2O3) better known for brilliant blue gemstones that dangle from ears and throats and can cost a small fortune.

But this particular screen bears little resemblance to Earth-mined rock. Synthetically grown from a "mother" or starter crystal, companies that manufacture synthetic sapphire melt and cut the material (with diamond-tipped saws) into wafers, sheets, you name it.

In the case of the demo, a thin sheet of sapphire has been glued over a regular iPhone 5's chemically hardened Gorilla Glass 2 screen with some transparent adhesive -- it's completely clear. To my eye, the sapphire overlay is indistinguishable from a pane of glass. That is, until I've spent a few minutes deliberately trying to scratch and smash it with a hunk of craggy concrete.

Most of the time, the only result was a building layer of concrete powder that coats the screen, but wipes away clean. One time a tiny nugget of concrete did break from the chunk and stick to the sapphire display. I thought perhaps it was embedded, but it flicked away without any noticeable nicks or indentations. Next to it in the demo, a sheet of Gorilla Glass collected scratches.

Depending on the exact formula of chemically reinforced glass, sapphire has approximately 2.5 or 3 times its strength.

Apart from being one of the strongest compound materials there is -- second only to the diamond that cuts it -- synthetic sapphire is highly rigid and won't buckle or melt in high-temperature situations. It is also slow to corrode, conducts heat at low temperatures, and is known for its excellent light transmission for wavelengths well beyond the scope of human vision. The screen was just as responsive as glass when I handled the device.

Grown sapphire is already used in aerospace, military, and medical devices -- especially lasers, protective windows, and highly specialized lenses. It's also used in LED TVs and bulbs, and the high-end watch industry, and it already existed in the iPhone 5 demo unit as a cover material for the main camera lens.

And yes, sapphire has already turned up in a smartphone, making its debut in the Vertu Ti Android phone, which sells for upward of $10,000. Luckily, most future smartphones with sapphire displays won't cost such a jaw-dropping bundle, although the material is more costly, about three or four times the cost of regular glass.

Related stories

Yet, cost is exactly why we're even able to conceive of sapphire as your phone's topper material. Manufacturing prices continue to drop -- it's all about economies of scale.

GT Advanced Technologies, the company that organized the sapphire display demo, manufactures the giant blocks, or boules, of crystalline sapphire that customers such as China's Zhejiang Shangcheng Science and Technology eventually turn into phone screens and more. It takes 16 days and a furnace at 2,200 degrees Celsius (almost 4,000 Fahrenheit) to create a 250-pound block of synthetic sapphire.

Today there's not enough capacity to create sapphire displays en masse, but we will see an uptick in adoption at the higher end of the spectrum. How much would you pay for a phone with a virtually indestructible screen?

About the author

Jessica Dolcourt reviews smartphones and cell phones, covers handset news, and pens the monthly column Smartphones Unlocked. A senior editor, she started at CNET in 2006 and spent four years reviewing mobile and desktop software before taking on devices.
See full bio